Phase tailoring for resonant flow devices

ABSTRACT

A device including a resonant array of a plurality of synthetic jet generators where neighboring jet generators are coupled, resulting in the potential for constructive and destructive interference between jets of the plurality of synthetic jet generators depending on the relative phase of a corresponding plurality of drive signals to plurality of synthetic jet generators. The device also includes a controller configured to control the relative phase of the corresponding plurality of drive signals to effect a change in a first jet emitted by a first synthetic jet generator of the plurality of synthetic jets by changing a given phase of a second jet emitted by a second synthetic jet generator of the plurality of synthetic jet generators.

BACKGROUND INFORMATION 1. Field

The present disclosure relates to array phasing to tailor spatialvelocity profiles of synthetic jets.

2. Background

In aerospace applications, synthetic jets are used to help an aircraftfly more efficiently. Synthetic jets are generally formed by forcing afluid flow through a small opening, typically in a pumped or cyclicmanner. Synthetic jets may also be produced by periodic ejection andsuction of the fluid from an opening or orifice, the ejection andsuction being induced by movement of a diaphragm inside a cavity.

SUMMARY

The illustrative embodiments provide for a device including a resonantarray of a plurality of synthetic jet generators, where neighboring jetgenerators are coupled, resulting in the potential for constructive anddestructive interference between jets of the plurality of synthetic jetgenerators depending on the relative phase of a corresponding pluralityof drive signals to the plurality of synthetic jet generators. Thedevice also includes a controller configured to control the relativephase of the corresponding plurality of drive signals to effect a changein a first jet emitted by a first synthetic jet generator of theplurality of synthetic jets by changing a given phase of a second jetemitted by a second synthetic jet generator of the plurality ofsynthetic jet generators.

The illustrative embodiments also provide for a device including a firstsynthetic jet generator configured to generate a first synthetic jet.The device also includes a second synthetic jet generator coupled to thefirst synthetic jet generator and configured to generate a secondsynthetic jet. The device also includes a controller coupled to both thefirst synthetic jet generator and the second synthetic jet generator.The controller is configured to transmit a first drive signal to thefirst synthetic jet generator. The controller is also configured totransmit a second drive signal to the second synthetic jet generator.The controller is also configured to control a combined operation of thefirst synthetic jet generator and the second synthetic jet generator bycontrolling a relative phase difference between the first drive signaland the second drive signal.

The illustrative embodiments also provide for a method. The methodincludes generating a first synthetic jet using a first synthetic jetgenerator. The method also includes generating a second synthetic jetusing a second synthetic jet generator that is coupled to the firstsynthetic jet generator. The method also includes controlling, using acontroller coupled to both the first synthetic jet generator and thesecond synthetic jet generator, the first synthetic jet and the secondsynthetic jet. Controlling includes transmitting a first drive signal tothe first synthetic jet generator. Controlling also includestransmitting a second drive signal to the second synthetic jetgenerator. Controlling also includes controlling a combined operationthe first synthetic jet and the second synthetic jet by adjusting aphase difference between the first drive signal and the second drivesignal.

The features and functions can be achieved independently in variousembodiments of the present disclosure or may be combined in yet otherembodiments in which further details can be seen with reference to thefollowing description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the illustrativeembodiments are set forth in the appended claims. The illustrativeembodiments, however, as well as a preferred mode of use, furtherobjectives and features thereof, will best be understood by reference tothe following detailed description of an illustrative embodiment of thepresent disclosure when read in conjunction with the accompanyingdrawings, wherein:

FIG. 1 is an illustration of a synthetic jet generator in accordancewith an illustrative embodiment;

FIG. 2 is an illustration of an application of velocity profiling of asynthetic jet in accordance with an illustrative embodiment;

FIG. 3 is another illustration of an application of velocity profilingof a synthetic jet in accordance with an illustrative embodiment;

FIG. 4 is an illustration of a graph of measured velocity variation withphase for a synthetic jet in accordance with an illustrative embodiment;

FIG. 5 is an illustration of an aircraft in accordance with anillustrative embodiment;

FIG. 6 is an illustration of a block diagram of a device including asynthetic jet generator in accordance with an illustrative embodiment;

FIG. 7 is another illustration of a block diagram of a device includinga synthetic jet generator in accordance with an illustrative embodiment;

FIG. 8 is an illustration of a flowchart of a method for operating asynthetic jet generator in accordance with an illustrative embodiment;and

FIG. 9 is an illustration of a block diagram of a detection system inaccordance with an illustrative embodiment.

DETAILED DESCRIPTION

The illustrative embodiments recognize and take into account that activeflow control (AFC) is technique used to modify the airflow over a wingor other body immersed in a fluid by injecting fluid momentum on or nearthe surface, such as, for example, an outer mold line of a wing. Activeflow control (AFC) allows for increased aerodynamic performance eitherin off-design conditions or on aerodynamic surfaces which were optimizedfor non-aerodynamic considerations, such as internal components,structural, and the like.

The illustrative embodiments also recognize and take into account that anumber of flow control actuators have been proposed to inject thismomentum into the flow. Historically, these systems have relied on ahigh pressure air supply, such as bleed air from an engine. As modernaircraft move to all-electric systems, this air supply is not readilyavailable. For that reason, the illustrative embodiments also recognizeand take into account that the all-electric synthetic jet actuator (SJA)of the illustrative embodiments is a particularly attractive option toachieve the flow control input.

An effective active flow control strategy, such as mitigating separationover a flap, may require adjustment of the actuation input over theactuated region. The actuation input distribution across the region maybe invariant in time, which is open loop actuation, but more likely willneed to be varied in response to changing aerodynamic conditions, whichis closed loop actuation.

The illustrative embodiments also recognize and take into account thatcurrent methods of adjusting actuation input require amplitude tailoringof the harmonic drive signal to the synthetic jet actuators. Theillustrative embodiments also recognize and take into account that thistype of control is an unattractive solution as it requires continuousadjustment of the gain of a set of high voltage signals, and it may notyield the desired velocity profile. Thus, the illustrative embodimentsprovide for a method of adjusting the spatial distribution of theactuation input by adjusting only the relative phase of the drive signalbetween jets, while operating at a constant voltage amplitude. Theconstant amplitude varying phase technique of the illustrativeembodiments is a potentially simpler electrical circuit.

The illustrative embodiments also recognize and take into account thatthe authors have observed, for an array of resonant synthetic jets, thatthe phase relationship between the drive signal to each of the actuatorsin the array can be used to tailor the velocity profile output of thearray. A related observation made by the authors is that activating oneof the synthetic jets in a resonant array will drive the neighboringsynthetic jets at nearly sixty percent of the amplitude of the activejet. The illustrative embodiments also recognize and take into accountthat these observations enable velocity profile shaping by controllingthe relative phase of constant amplitude drive signals to a resonantarray of jets.

Stated differently, the illustrative embodiments provide for an array ofresonant synthetic jets, wherein the phase relationship between thedrive signal to each of the actuators in the array can be used to tailorthe velocity profile output of the array. As noted above, activating oneof the synthetic jets in a resonant array will drive the neighboringsynthetic jets at nearly sixty percent of the amplitude of the activejet. These observations enable velocity profile shaping by controllingthe relative phase of constant amplitude drive signals to a resonantarray of jets.

As indicated above, the illustrative embodiments recognize and take intoaccount that active flow control actuators may be adjusted to ensureeffective performance and airflow control. Continuous adjustment of thegain of a set of high voltage signals may be required, and it may notyield the desired velocity profile. The adjustment can be accomplishedonce prior to installation (standard adjustment) or in real time.

As indicated above, adjusting actuation input of resonant flow controlactuators (jets) requires amplitude tailoring to control the harmonicdrive signal to the synthetic jet actuators. Also as indicated above,this technique is an unattractive solution as it requires continuousadjustment of the gain of a set of high voltage signals, and it may notyield the desired velocity profile.

As indicated above, the illustrative embodiments solve the issuesdescribed above by providing for a method of adjusting the spatialdistribution of the actuation input by adjusting only the relative phaseof the drive signal between jets, while operating at a constant voltageamplitude. Constant amplitude varying phase can be a simpler electricalcircuit. For example, the phase adjustment may be accomplished with adigital delay or an analog circuit, such as a bridged-T delay equalizer.Other simple electrical circuits could be used. The authors havedetermined that it is easier to create a set of driven voltage signalsthat have the same amplitude and different phases, as opposed tocreating a signal with the same phase and different voltages. Thus, theillustrative embodiments provide for phase tailoring for resonant flowdevices.

FIG. 1 is an illustration of a synthetic jet generator in accordancewith an illustrative embodiment. Synthetic jet generator array 100 mayinclude any of a number of, either custom or commercially available,synthetic jet generators. Synthetic jet generator array 100 includesline of synthetic jet generators 102, which in FIG. 1 has synthetic jetgenerator 104 and synthetic jet generator 106. Multiple additionalsynthetic jet generators may be present in line of synthetic jetgenerators 102, including but not limited to synthetic jet generator108, synthetic jet generator 110, synthetic jet generator 112, syntheticjet generator 114, and synthetic jet generator 116.

Each synthetic jet generator is controlled using controller 118. Eachsynthetic jet generator may include an individual actuator, such asactuator 120 of synthetic jet generator 106. The actuators, such asactuator 120, drive the synthetic jets, typically by pumping adiaphragm, which in turn forces air into and out of synthetic jetgenerator 106. Typically, air or other fluid is forced through anaperture, such as aperture 122 of synthetic jet generator 106. Becausethe air is forced in and out at high velocity and at high frequency,repeating jets of air are forced out of aperture 122, with air drawninto aperture 122 between periods when air is forced out of aperture122. Because of the frequency of repetition, to human perception, asingle apparently continuous jet is formed. However, in actuality,multiple jets are ejected from aperture 122 at a high frequency. It isfor this reason that these devices are referred to as “synthetic” jetgenerators.

The illustrative embodiments disclosed herein are directed towardscontrolling multiple linked synthetic jet generators, not towards anygiven single synthetic jet generator. In particular, the illustrativeembodiments recognize and take into account that when linked syntheticjet generators are driven by a single controller, changing the phase ofthe electrical signal that drives the linked synthetic jet generatorscan change how any given synthetic jet generator operates. Thus, theillustrative embodiments provide for phase tailoring for resonant flowdevices. This effect and how to control it are described further belowwith respect to FIG. 4 through FIG. 8.

FIG. 2 is an illustration of an application of velocity profiling of asynthetic jet in accordance with an illustrative embodiment. FIG. 3 isanother illustration of an application of velocity profiling of asynthetic jet in accordance with an illustrative embodiment. FIG. 2 andFIG. 3 should be considered together, and are variants of each other.

In an illustrative embodiment, velocity measurements of fluid flow 200across air foil 202 were made using an array of two closely matchedresonant synthetic jets, which could be, for example, synthetic jetgenerator 104 and synthetic jet generator 106 of FIG. 1.

The drive signal amplitude is the same for both synthetic jetgenerators, but the relative phase is changed from zero to 360 degreesin fifteen degree increments. This data is plotted in FIG. 4, below. Atthe initial phase of zero, a stall started to occur in the velocityprofile, as indicated by area 204 of profile 206. However, bycontrolling the phase of the drive signal to the two synthetic jetgenerators, the synthetic jet velocity profile is changed to profile208. Profile 208 is smoother than profile 206, and thus is consideredmore desirable for aerodynamic performance, such as air flow over thewing of an aircraft.

Likewise, in an illustrative embodiment, velocity measurements of fluidflow 300 across air foil 302 were made using an array of two closelymatched resonant synthetic jets, which could be, for example, syntheticjet generator 104 and synthetic jet generator 106 of FIG. 1.

The drive signal amplitude is the same for both synthetic jetgenerators, but the relative phase is changed from 360 to zero degreesin fifteen degree increments. This data is plotted in FIG. 4, below. Atthe initial phase of 360, a stall started to occur in the velocityprofile, as indicated by area 304 of profile 306. However, bycontrolling the phase of the drive signal to the two synthetic jetgenerators, the synthetic jet velocity profile is changed to profile308. Profile 308 is smoother than profile 306, and thus is consideredmore desirable for aerodynamic performance, such as air flow over thewing of an aircraft.

FIG. 4 is an illustration of a graph of measured velocity variation withphase for a synthetic jet, in accordance with an illustrativeembodiment. Graph 400 may be an example of data that results whensynthetic jets, such as those in FIG. 1, are directed across an airfoil, such as airfoil 202 and airfoil 302 in FIG. 2 and FIG. 3,respectively.

Graph 400 is a graph of peak jet velocity measured in meters per second,as shown on vertical axis 404, versus phase angle between jet drivingsignals in degrees, as shown on horizontal axis 402. Line 406 representsa single active jet, that being jet A of synthetic jet generator A. Line408 represent a single active jet, that being jet B from synthetic jetgenerator B. Line 410 represents both jet A and jet B being active, andthe effect on jet A of varying the phase of the drive signal onsynthetic jet generator B. Line 412 represents both jet A and jet Bbeing active, and the effect on jet B of varying the phase of the drivesignal on synthetic jet generator A.

From graph 400, it is clear that the peak in velocity amplitude for jetA or jet B can be increased from a minimum of 12 m/s to a maximum of 36m/s by adjusting the phase to 90 degrees or 270 degrees. It is also ofinterest to note that when the drive signal is applied to one of thejets resulting with an amplitude of 24 m/s, the other jet has anamplitude of 15 m/s with no drive signal. It is this coupling betweenresonant jets, that result in the ability to tailor the velocityprofiles with phase. Finally, it is worth noting that at multiples of180 degrees of phase, the velocity of each of the jets is around 27 m/s,which is noticeably higher than the 24 m/s achievable by a single jet.

Similar velocity profiling with a non-resonant, non-coupled array wouldrequire a higher power input to drive the device, indicating that thechange in coupling with relative phase angles corresponds to a change indevice efficiency, which is the jets' ability to convert electricalpower into fluid power. Moreover, any realistic installation ofsynthetic jet actuators will inherently require mechanical coupling ofadjacent actuators, which will cause this “crosstalk”. Ignoring thephase relationship between devices may lead to unnecessarily diminishedperformance for any given power input.

The illustrative embodiments described herein may be varied. Forexample, this concept may be extended to any resonant flow device inwhich mechanical coupling exists between adjacent modules.

FIG. 5 is an illustration of an aircraft, in accordance with anillustrative embodiment. Aircraft 500 includes wing 502 and wing 504attached to fuselage 506, engine 508 attached to wing 502, and engine510 attached to wing 504. Engine 510 could also be attached to fuselage506. Fuselage 506 has tail section 512. Horizontal stabilizer 514,horizontal stabilizer 516, and vertical stabilizer 518 are attached totail section 512 of fuselage 506.

A computer, such as data processing system 900 of FIG. 9, may be insidefuselage 506, in a cabin or cockpit, for example. This computer maystore program code for executing any of the methods or techniquesdescribed, above or below, in order to automatically operate aircraft500 using a synthetic jet generator, such as synthetic jet generator520. The operation of synthetic jet generator 520 may be based on inputprovided by sensor 522, or some other sensor. For example, sensor 522may be configured to detect local aerodynamic stall characteristics of afluid flow on the body of aircraft 500.

Synthetic jet generator 520 may be any of the synthetic jet generatorsdescribed with respect to FIG. 1 through FIG. 4, or FIG. 5 and FIG. 6.Method 800 of FIG. 8 may be performed by synthetic jet generator 520.The purpose of synthetic jet generator 520 may be to aid aircraft 500 tofly more efficiently, such as by affecting the airflow around wing 502or wing 504 in a manner that increases fuel efficiency, maneuverability,or both.

FIG. 6 is an illustration of a block diagram of a device including asynthetic jet generator, in accordance with an illustrative embodiment.Device 600 may be an example of a set of synthetic jet generators, suchas those shown in FIG. 1.

Device 600 includes a resonant array of plurality of synthetic jetgenerators 602 where neighboring synthetic jet generators are coupled,resulting in the potential for constructive and destructive interferencebetween the jets of plurality of synthetic jet generators 602 dependingon relative phase 604 of corresponding plurality of drive signals 606 toplurality of synthetic jet generators 602. Device 600 also includescontroller 608, configured to control relative phase 604 ofcorresponding plurality of drive signals 606 to effect a change in afirst jet emitted by first synthetic jet generator 610 of plurality ofsynthetic jets generators 602 by changing a given phase of a second jetemitted by second synthetic jet generator 612 of plurality of syntheticjet generators 602.

Device 600 may be varied. For example, in an illustrative embodiment,the given phase may be configured to cause a larger amplitude in each ofthe jets than what is possible with a single jet. In anotherillustrative embodiment, a resulting velocity profile of the jets isshaped depending on the relative phases to each jet generator ofplurality of synthetic jet generators 602. In still another illustrativeembodiment, the second jet will only change when first synthetic jetgenerator 610 is driven.

In yet another illustrative embodiment, device 600 also includes anaircraft, such as aircraft 500 shown in FIG. 5. Aircraft 500 may beconnected to plurality of synthetic jet generators 602. A sensor, suchas sensor 522 of FIG. 5, may be connected to aircraft 500 and configuredto detect local aerodynamic stall characteristics of a fluid flow on thebody of aircraft 500. In this case, controller 608 may be furtherconfigured to adjust the first jet by changing a phase angle of thesecond jet generator to mitigate the local aerodynamic stallcharacteristics.

The illustrative embodiments described with respect to FIG. 6 may befurther varied. Thus, the illustrative embodiments described withrespect to FIG. 6 do not necessarily limit the claimed inventions.

FIG. 7 is another illustration of a block diagram of a device includinga synthetic jet generator in accordance with an illustrative embodiment.Device 700 is a variation of any of the synthetic jet generators ofsynthetic jet generator array 100 of FIG. 1, or synthetic jet generator600 of FIG. 6.

Device 700 includes first synthetic jet generator 702 configured togenerate a first synthetic jet. Device 700 also includes secondsynthetic jet generator 704 coupled to first synthetic jet generator 702and configured to generate a second synthetic jet.

Device 700 also includes controller 706 coupled to both first syntheticjet generator 702 and second synthetic jet generator 704. Controller 706may be configured to transmit first drive signal 708 to first syntheticjet generator 702. Controller 706 also may be configured to transmitsecond drive signal 710 to second synthetic jet generator 704.Controller 706 also may be configured to control a combined operation ofboth first synthetic jet generator 702 and second synthetic jetgenerator 704 by controlling relative phase difference 712 between firstdrive signal 708 and second drive signal 710.

Device 700 may be varied. For example, in an illustrative embodiment thecontroller is further configured to control the operation of firstsynthetic jet generator 702 by controlling only relative phasedifference 712. In a related illustrative embodiment, controller 706 maybe further configured to control operation of first synthetic jetgenerator 702 by transmitting only second drive signal 710. In anotherrelated illustrative embodiment, device 700 also includes feedbackcircuit 714. Feedback circuit 714 may be coupled to first synthetic jetgenerator 702, second synthetic jet generator 704, and controller 706.In this case, controller 706 may be further configured to use a feedbacksignal from feedback circuit 714 to control first synthetic jetgenerator 702 and second synthetic jet generator 704 to produce apredetermined velocity profile of a combination of the first syntheticjet generator and the second synthetic jet generator.

In a related illustrative embodiment, device 700 may also include ahousing containing the first synthetic jet generator, the secondsynthetic jet generator, and the controller. The housing may be, forexample, synthetic jet generator 520 of FIG. 5. In this case, device 700also includes an aircraft connected to the housing. The aircraft may beaircraft 500 of FIG. 5. Additionally, device 700 may also include asensor connected to the aircraft and configured to detect localaerodynamic stall characteristics of a fluid flow on a body of theaircraft. The sensor may be sensor 522 of FIG. 5. In this case, thecontroller is further configured to mitigate the local aerodynamic stallcharacteristics by producing the predetermined velocity profile.

In a different illustrative embodiment, controller 706 is furtherconfigured to drive both first synthetic jet generator 702 and secondsynthetic jet generator 704 at a single constant voltage amplitude. Inanother illustrative embodiment, controller 706 may be furtherconfigured to increase both a first maximum velocity of the firstsynthetic jet and a second maximum velocity of the second synthetic jetby changing relative phase difference 712. In this case, relative phasedifference 712 may be about 180 degrees. However, relative phasedifference 712 may be any value between zero and 360 degrees.

The illustrative embodiments described with respect to FIG. 7 may befurther varied. Thus, the illustrative embodiments described withrespect to FIG. 7 do not necessarily limit the claimed invention.

FIG. 8 is an illustration of a flowchart of a method for operating asynthetic jet generator in accordance with an illustrative embodiment.Method 800 may be implemented using two or more synthetic jetgenerators, such as synthetic jet generator array 100 of FIG. 1, device600 of FIG. 6, or device 700 of FIG. 7.

Method 800 includes generating a first synthetic jet using a firstsynthetic jet generator (operation 802). Method 800 then includesgenerating a second synthetic jet using a second synthetic jet generatorthat is coupled to the first synthetic jet generator (operation 804).Method 800 then includes controlling, using a controller coupled to boththe first synthetic jet generator and the second synthetic jetgenerator, the first synthetic jet and the second synthetic jet(operation 806).

In method 800, controlling includes transmitting a first drive signal tothe first synthetic jet generator (operation 808). In method 800,controlling also includes transmitting a second drive signal to thesecond synthetic jet generator (operation 810). In method 800,controlling also includes controlling a combined operation of the firstsynthetic jet and the second synthetic jet by adjusting a phasedifference between the first drive signal and the second drive signal(operation 812). In one illustrative embodiment, the method mayterminate thereafter.

Method 800 may be varied. For example, the controller may be furtherconfigured to control operation of the first synthetic jet generator bycontrolling only the phase difference. In another illustrativeembodiment, method 800 may also include producing a predeterminedvelocity profile of a combination of the first synthetic jet and thesecond synthetic jet using a feedback signal from a feedback circuit,the feedback circuit coupled to the first synthetic jet generator, thesecond synthetic jet generator, and the controller.

In this case, method 800 may also include detecting, using a sensorconnected to an aircraft, local aerodynamic stall characteristics of afluid flow on a body of the aircraft. Then, method 800 may also includemitigating, using the combined operation of the first synthetic jet andthe second synthetic jet, the local aerodynamic stall characteristics byproducing the predetermined velocity profile.

In another illustrative embodiment, method 800 may also include drivingboth the first synthetic jet generator and the second synthetic jetgenerator at a single constant voltage amplitude. In still anotherillustrative embodiment, method 800 may also include increasing both afirst maximum velocity of the first synthetic jet and a second maximumvelocity of the second synthetic jet by changing the relative phase. Inone specific example, the relative phase may be about one hundred andeighty degrees. However, the relative phase may vary between zerodegrees and 360 degrees.

The illustrative embodiments described with respect to FIG. 8 may befurther varied. Thus, the illustrative embodiments described withrespect to FIG. 8 do not necessarily limit the claimed invention.

Turning now to FIG. 9, an illustration of a data processing system isdepicted in accordance with an illustrative embodiment. Data processingsystem 900 in FIG. 9 is an example of a data processing system that maybe used to in conjunction with the illustrative embodiments, such asline of synthetic jet generators 102 of FIG. 1, or any other device ortechnique disclosed herein. In this illustrative example, dataprocessing system 900 includes communications fabric 902, which providescommunications between processor unit 904, memory 906, persistentstorage 908, communications unit 910, input/output unit 912, and display914.

Processor unit 904 serves to execute instructions for software that maybe loaded into memory 906. This software may be an associative memory,which is a type of content addressable memory, or software forimplementing the processes described herein. Thus, for example, softwareloaded into memory 906 may be software for executing method 800 of FIG.8, or for executing techniques described with respect to FIG. 1 throughFIG. 7.

Processor unit 904 may be a number of processors, a multi-processorcore, or some other type of processor, depending on the particularimplementation. A number, as used herein with reference to an item,means one or more items. Further, processor unit 904 may be implementedusing a number of heterogeneous processor systems in which a mainprocessor is present with secondary processors on a single chip. Asanother illustrative example, processor unit 904 may be a symmetricmulti-processor system containing multiple processors of the same type.

Memory 906 and persistent storage 908 are examples of storage devices916. A storage device is any piece of hardware that is capable ofstoring information, such as, for example, without limitation, data,program code in functional form, and/or other suitable information,either on a temporary basis and/or a permanent basis. Storage devices916 may also be referred to as computer-readable storage devices inthese examples. Memory 906, in these examples, may be, for example, arandom access memory or any other suitable volatile or non-volatilestorage device. Persistent storage 908 may take various forms, dependingon the particular implementation.

For example, persistent storage 908 may contain one or more componentsor devices. For example, persistent storage 908 may be a hard drive, aflash memory drive, a rewritable optical disk, a rewritable magnetictape, or some combination of the above mentioned devices. The media usedby persistent storage 908 also may be removable. For example, aremovable hard drive may be used for persistent storage 908.

Communications unit 910, in these examples, provides for communicationswith other data processing systems or devices. In these examples,communications unit 910 is a network interface card. Communications unit910 may provide communications through the use of either physical orwireless communications links, or both.

Input/output unit 912 allows for input and output of data with otherdevices that may be connected to data processing system 900. Forexample, input/output unit 912 may provide a connection for user inputthrough a keyboard, a mouse, and/or some other suitable type of inputdevice. Further, input/output unit 912 may send output to a printer.Display 914 provides a mechanism to display information to a user.

Instructions for the operating system, applications, and/or programs maybe located in storage devices 916, which are in communication withprocessor unit 904 through communications fabric 902. In theseillustrative examples, the instructions are in a functional form onpersistent storage 908. These instructions may be loaded into memory 906for execution by processor unit 904. The processes of the differentembodiments may be performed by processor unit 904 using computerimplemented instructions, which may be located in a memory, such asmemory 906.

These instructions are referred to as program code, computer-useableprogram code, or computer-readable program code that may be read andexecuted by a processor in processor unit 904. The program code in thedifferent embodiments may be embodied on different physical orcomputer-readable storage media, such as memory 906 or persistentstorage 908.

Computer-usable program code 918 is located in a functional form oncomputer-readable media 920 that is selectively removable and may beloaded onto or transferred to data processing system 900 for executionby processor unit 904. Computer-usable program code 918 andcomputer-readable media 920 form computer program product 922 in theseexamples. In one example, computer readable media 920 may becomputer-readable storage media 924 or computer-readable signal media926. Computer-readable storage media 924 may include, for example, anoptical or magnetic disk that is inserted or placed into a drive orother device that is part of persistent storage 908 for transfer onto astorage device, such as a hard drive, that is part of persistent storage908. Computer-readable storage media 924 also may take the form of apersistent storage, such as a hard drive, a thumb drive, or a flashmemory, that is connected to data processing system 900. In someinstances, computer-readable storage media 924 may not be removable fromdata processing system 900.

Alternatively, computer-usable program code 918 may be transferred todata processing system 900 using computer-readable signal media 926.Computer-readable signal media 926 may be, for example, a propagateddata signal containing computer-usable program code 918. For example,computer-readable signal media 926 may be an electromagnetic signal, anoptical signal, and/or any other suitable type of signal. These signalsmay be transmitted over communications links, such as wirelesscommunications links, optical fiber cable, coaxial cable, a wire, and/orany other suitable type of communications link. In other words, thecommunications link and/or the connection may be physical or wireless inthe illustrative examples.

In some illustrative embodiments, computer-usable program code 918 maybe downloaded over a network to persistent storage 908 from anotherdevice or data processing system through computer-readable signal media926 for use within data processing system 900. For instance, programcode stored in a computer-readable storage medium in a server dataprocessing system may be downloaded over a network from the server todata processing system 900. The data processing system providingcomputer-usable program code 918 may be a server computer, a clientcomputer, or some other device capable of storing and transmittingcomputer-usable program code 918.

The different components illustrated for data processing system 900 arenot meant to provide architectural limitations to the manner in whichdifferent embodiments may be implemented. The different illustrativeembodiments may be implemented in a data processing system includingcomponents, in addition to or in place of those, illustrated for dataprocessing system 900. Other components shown in FIG. 9 can be variedfrom the illustrative examples shown. The different embodiments may beimplemented using any hardware device or system capable of runningprogram code. As one example, the data processing system may includeorganic components integrated with inorganic components and/or may becomprised entirely of organic components, excluding a human being. Forexample, a storage device may be comprised of an organic semiconductor.

In another illustrative example, processor unit 904 may take the form ofa hardware unit that has circuits that are manufactured or configuredfor a particular use. This type of hardware may perform operationswithout needing program code to be loaded into a memory from a storagedevice to be configured to perform the operations.

For example, when processor unit 904 takes the form of a hardware unit,processor unit 904 may be a circuit system, an application specificintegrated circuit (ASIC), a programmable logic device, or some othersuitable type of hardware configured to perform a number of operations.With a programmable logic device, the device is configured to performthe number of operations. The device may be reconfigured at a later timeor may be permanently configured to perform the number of operations.Examples of programmable logic devices include, for example, aprogrammable logic array, programmable array logic, a field programmablelogic array, a field programmable gate array, or other suitable types ofhardware devices. With this type of implementation, computer-usableprogram code 918 may be omitted because the processes for the differentembodiments are implemented in a hardware unit.

In still another illustrative example, processor unit 904 may beimplemented using a combination of processors found in computers andhardware units. Processor unit 904 may have a number of hardware unitsand a number of processors that are configured to run computer-usableprogram code 918. With this depicted example, some of the processes maybe implemented in the number of hardware units, while other processesmay be implemented in the number of processors.

As another example, a storage device in data processing system 900 isany hardware apparatus that may store data. Memory 906, persistentstorage 908, and computer-readable media 920 are examples of storagedevices in a tangible form.

In another example, a bus system may be used to implement communicationsfabric 902 and may be comprised of one or more buses, such as a systembus or an input/output bus. Of course, the bus system may be implementedusing any suitable type of architecture that provides for a transfer ofdata between different components or devices attached to the bus system.Additionally, a communications unit may include one or more devices usedto transmit and receive data, such as a modem or a network adapter.Further, a memory may be, for example, a cache. A memory may also bememory 906, found in an interface and memory controller hub that may bepresent in communications fabric 902.

Data processing system 900 may also include an associative memory. Anassociative memory may be in communication with communications fabric902. An associative memory may also be in communication with, or in someillustrative embodiments, be considered part of storage devices 916.Additional associative memories may be present.

As used herein, the term “associative memory” refers to a plurality ofdata and a plurality of associations among the plurality of data. Theplurality of data and the plurality of associations may be stored in anon-transitory computer-readable storage medium. The plurality of datamay be collected into associated groups. The associative memory may beconfigured to be queried based on at least indirect relationships amongthe plurality of data, in addition to direct correlations among theplurality of data. Thus, an associative memory may be configured to bequeried based solely on direct relationships, based solely on at leastindirect relationships, as well as based on combinations of direct andindirect relationships. An associative memory may be a contentaddressable memory.

Thus, an associative memory may be characterized as a plurality of dataand a plurality of associations among the plurality of data. Theplurality of data may be collected into associated groups. Further, theassociative memory may be configured to be queried based on at least onerelationship, selected from a group that includes direct and indirectrelationships, or from among the plurality of data, in addition todirect correlations among the plurality of data. An associative memorymay also take the form of software. Thus, an associative memory also maybe considered a process by which information is collected intoassociated groups in the interest of gaining new insight based onrelationships rather than direct correlation. An associative memory mayalso take the form of hardware, such as specialized processors or afield programmable gate array.

As used herein, the term “entity” refers to an object that has adistinct, separate existence, though such existence need not be amaterial existence. Thus, abstractions and legal constructs may beregarded as entities. As used herein, an entity need not be animate.Associative memories work with entities.

The different illustrative embodiments can take the form of an entirelyhardware embodiment, an entirely software embodiment, or an embodimentcontaining both hardware and software elements. Some embodiments areimplemented in software, which include but are not limited to forms suchas, for example, firmware, resident software, and microcode.

Furthermore, the different embodiments can take the form of a computerprogram product accessible from a computer-usable or computer-readablemedium providing program code for use by or in connection with acomputer or any device or system that executes instructions. For thepurposes of this disclosure, a computer-usable or computer-readablemedium can generally be any tangible apparatus that can contain, store,communicate, propagate, or transport the program for use by or inconnection with the instruction execution system, apparatus, or device.

The computer-usable or computer-readable medium can be, for example,without limitation an electronic, magnetic, optical, electromagnetic,infrared, or semiconductor system, or a propagation medium. Non-limitingexamples of a computer-readable medium include a semiconductor or solidstate memory, magnetic tape, a removable computer diskette, a randomaccess memory (RAM), a read-only memory (ROM), a rigid magnetic disk,and an optical disk. Optical disks may include compact disk read-onlymemory (CD-ROM), compact disk-read/write (CD-R/W), or DVD.

Further, a computer-usable or computer-readable medium may contain orstore a computer-readable or computer-usable program code, such thatwhen the computer-readable or computer-usable program code is executedon a computer, the execution of this computer-readable orcomputer-usable program code causes the computer to transmit anothercomputer-readable or computer-usable program code over a communicationslink. This communications link may use a medium that is, for examplewithout limitation, physical or wireless.

A data processing system suitable for storing and/or executingcomputer-readable or computer-usable program code will include one ormore processors coupled, directly or indirectly, to memory elementsthrough a communications fabric, such as a system bus. The memoryelements may include local memory employed during actual execution ofthe program code, bulk storage, and cache memories which providetemporary storage of at least some computer-readable or computer-usableprogram code to reduce the number of times code may be retrieved frombulk storage during execution of the code.

Input/output unit or input/output devices can be coupled to the systemeither directly or through intervening input/output controllers. Thesedevices may include, for example, without limitation, keyboards, touchscreen displays, or pointing devices. Different communications adaptersmay also be coupled to the system to enable the data processing systemto become coupled to other data processing systems, remote printers, orstorage devices through intervening private or public networks.Non-limiting examples of modems and network adapters are just a few ofthe currently available types of communications adapters.

The description of the different illustrative embodiments has beenpresented for purposes of illustration and description, and is notintended to be exhaustive or limited to the embodiments in the formdisclosed. Many modifications and variations will be apparent to thoseof ordinary skill in the art. Further, different illustrativeembodiments may provide different features as compared to otherillustrative embodiments. The embodiment or embodiments selected arechosen and described in order to best explain the principles of theembodiments, the practical application, and to enable others of ordinaryskill in the art to understand the disclosure for various embodimentswith various modifications as are suited to the particular usecontemplated.

What is claimed is:
 1. A device comprising: a resonant array of aplurality of synthetic jet generators where neighboring jet generatorsare coupled, resulting in the potential for constructive and destructiveinterference between jets of the plurality of synthetic jet generatorsdepending on a relative phase of a corresponding plurality of drivesignals to the plurality of synthetic jet generators; and a controllerconfigured to control the relative phase of the corresponding pluralityof drive signals to effect a change in a first jet emitted by a firstsynthetic jet generator of the plurality of synthetic jet generators bychanging a given phase of a second jet emitted by a second synthetic jetgenerator of the plurality of synthetic jet generators.
 2. The device ofclaim 1, wherein the given phase is configured to cause a largeramplitude in each of the jets than is possible with a single jet.
 3. Thedevice of claim 1, wherein a resulting velocity profile of the jets isshaped depending on the relative phases to each jet generator of theplurality of synthetic jet generators.
 4. The device of claim 1, whereinthe second jet will only change when the first synthetic jet generatoris driven.
 5. The device of claim 1 further comprising: an aircraftconnected to the plurality of synthetic jet generators; and a sensorconnected to the aircraft and configured to detect local aerodynamicstall characteristics of a fluid flow on a body of the aircraft, andwherein the controller is further configured to adjust the first jet bychanging a phase angle of the second jet generator to mitigate the localaerodynamic stall characteristics.
 6. A device comprising: a firstsynthetic jet generator configured to generate a first synthetic jet; asecond synthetic jet generator coupled to the first synthetic jetgenerator and configured to generate a second synthetic jet; acontroller coupled to both the first synthetic jet generator and thesecond synthetic jet generator, wherein the controller is configured to:transmit a first drive signal to the first synthetic jet generator;transmit a second drive signal to the second synthetic jet generator;and control a combined operation of the first synthetic jet generatorand the second synthetic jet generator by controlling a relative phasedifference between the first drive signal and the second drive signal.7. The device of claim 6, wherein the controller is further configuredto control operation of the first synthetic jet generator by controllingonly the relative phase difference.
 8. The device of claim 6, whereinthe controller is further configured to control operation of the firstsynthetic jet generator by transmitting only the second drive signal. 9.The device of claim 6 further comprising: a feedback circuit coupled tothe first synthetic jet generator, the second synthetic jet generator,and the controller, and wherein the controller is further configured touse a feedback signal from the feedback circuit to control the firstsynthetic jet generator and the second synthetic jet generator toproduce a predetermined velocity profile of a combination of the firstsynthetic jet and the second synthetic jet.
 10. The device of claim 9further comprising: a housing containing the first synthetic jetgenerator, the second synthetic jet generator, and the controller; anaircraft connected to the housing; and a sensor connected to theaircraft and configured to detect local aerodynamic stallcharacteristics of a fluid flow on a body of the aircraft, and whereinthe controller is further configured to mitigate the local aerodynamicstall characteristics by producing the predetermined velocity profile.11. The device of claim 6, wherein the controller is further configuredto drive both the first synthetic jet generator and the second syntheticjet generator at a single constant voltage amplitude.
 12. The device ofclaim 6, wherein the controller is further configured to increase both afirst maximum velocity of the first synthetic jet and a second maximumvelocity of the second synthetic jet by changing the relative phasedifference.
 13. The device of claim 12, wherein the relative phasedifference is about one hundred and eighty degrees.
 14. A methodcomprising: generating a first synthetic jet using a first synthetic jetgenerator; generating a second synthetic jet using a second syntheticjet generator that is coupled to the first synthetic jet generator;controlling, using a controller coupled to both the first synthetic jetgenerator and the second synthetic jet generator, the first syntheticjet and the second synthetic jet, wherein controlling includes:transmitting a first drive signal to the first synthetic jet generator;transmitting a second drive signal to the second synthetic jetgenerator; and controlling a combined operation of the first syntheticjet and the second synthetic jet by adjusting a phase difference betweenthe first drive signal and the second drive signal.
 15. The method ofclaim 14, wherein the controller is further configured to controloperation of the first synthetic jet generator by controlling only thephase difference.
 16. The method of claim 14 further comprising:producing a predetermined velocity profile of a combination of the firstsynthetic jet and the second synthetic jet using a feedback signal froma feedback circuit, the feedback circuit coupled to the first syntheticjet generator, the second synthetic jet generator, and the controller.17. The method of claim 16 further comprising: detecting, using a sensorconnected to an aircraft, local aerodynamic stall characteristics of afluid flow on a body of the aircraft; and mitigating, using a combinedoperation of the first synthetic jet and the second synthetic jet, thelocal aerodynamic stall characteristics by producing the predeterminedvelocity profile.
 18. The method of claim 14 further comprising: drivingboth the first synthetic jet generator and the second synthetic jetgenerator at a single constant voltage amplitude.
 19. The method ofclaim 14 further comprising: increasing both a first maximum velocity ofthe first synthetic jet and a second maximum velocity of the secondsynthetic jet by changing the phase difference.
 20. The method of claim19, wherein the phase difference is about one hundred and eightydegrees.